Labs to Check for Testosterone Replacement Therapy
Testosterone replacement therapy (TRT) is only as good as the monitoring behind it. Symptoms matter, but labs are what let us confirm dose adequacy, reduce side effects, and identify cardiometabolic risk factors that often coexist with low testosterone. These are labs we use for many of our patients. We structure labs into three groups: general hormone profiling, safety monitoring, and cardiometabolic risk and recovery markers.
General Labs
Total and free testosterone are the core efficacy measures. Total testosterone reflects overall exposure, while free testosterone better reflects bioavailable hormone, especially when SHBG is high or low. We interpret these in context of your dosing schedule so we can avoid excessive peaks and low troughs that can drive mood swings, fatigue, or libido variability.
Estradiol helps explain changes in libido, erectile quality, mood, sleep, water retention, and nipple sensitivity. Estradiol is not automatically "bad" on TRT, in fact, a lot of the positive effects of testosterone come through an increase in estrogen. The goal is an appropriate balance that matches symptoms and avoids extremes in either direction. Typically a 20:1-30:1 ratio of testosterone (ng/mL) to estradiol (pg/mL) is desirable.
FSH and LH help define the physiology of hypogonadism. They clarify whether low testosterone is driven more by testicular underproduction versus reduced pituitary signaling, and they inform fertility counseling and whether additional evaluation is appropriate.
Androstenedione and DHEA-S provide information about adrenal androgen production and androgen precursors. These can matter in men with persistent fatigue, low drive, atypical androgen profiles, or when we are trying to understand why symptoms do not match testosterone level.
Dihydrotestosterone (DHT) is a potent androgen generated from testosterone through conversion by the 5-alpha-reductase enzyme. DHT is relevant to scalp hair loss patterns, acne, prostate symptoms, and sometimes sexual function. Measuring DHT can help guide dose timing decisions and risk discussions in patients sensitive to androgenic effects.
IGF-1 provides a window into growth hormone axis signaling and overall anabolic milieu. It can be helpful when recovery is poor, lean mass response to training is blunted, or there are broader endocrine concerns.
Inhibin B is a marker related to Sertoli cell function and spermatogenesis. This is most useful when fertility is a priority or when we want a better baseline read on testicular function.
Pregnenolone, progesterone, 17-OH pregnenolone, and 17-OH progesterone are upstream steroid hormones and intermediates. In select patients they help assess steroidogenesis patterns, adrenal contributions, and rare enzyme pathway issues. They are not “routine TRT titration” labs, but they can be valuable when symptoms or prior results suggest an atypical endocrine pattern.
Prostate specific antigen (PSA) is used to track prostate health over time. We watch trends rather than single values and respond to unexpected changes with repeat testing and referral when indicated.
Safety Monitoring
CBC is essential because TRT can increase red blood cell production. We monitor hemoglobin and hematocrit to reduce the risk of hyperviscosity related symptoms and to guide adjustments in dose or dosing frequency.
Comprehensive metabolic panel (CMP) assesses liver enzymes, electrolytes, glucose, and kidney markers. This helps us identify issues that affect performance and recovery, such as dehydration, training related enzyme elevations, or underlying metabolic strain.
Cystatin C is useful for kidney filtration assessment, especially in muscular patients or those taking creatine, where creatinine based kidney assessments can be misleading. It helps us separate true kidney risk from benign creatinine elevation.
Cardiometabolic factors
High sensitivity C reactive protein (hs-CRP) is a marker of low grade systemic inflammation and cardiovascular risk. It also tracks recovery burden from sleep loss, stress, excess visceral fat, and overtraining.
CardioIQ lipid panel with ApoB assesses atherogenic particle burden. ApoB is often a better reflection of cardiovascular risk than LDL alone and helps guide how aggressive we should be with nutrition, training, and medications when needed.
Lipoprotein(a) is largely genetic and can substantially raise lifetime cardiovascular risk. Checking it helps us stratify risk and set tighter targets for ApoB and other modifiable factors.
Hemoglobin A1C reflects average glucose exposure and insulin resistance risk. This is central in men pursuing fat loss or metabolic optimization, and it often improves with consistent training and nutrition changes.
Leptin reflects energy balance and fat mass signaling and can help explain appetite dysregulation, "food noise," and weight loss plateaus in some patients. It is most useful when interpreted alongside body composition and insulin resistance markers.
Thyroid panels evaluate thyroid function, which strongly influences energy, mood, lipids, and body composition response. Suboptimal thyroid function can blunt progress even when testosterone is optimized.
Vitamin D supports musculoskeletal health, immune function, and overall performance. We use it to identify deficiency and guide repletion targets, especially in patients with pain syndromes, low recovery capacity, or low sun exposure.
How We Use These Labs in Practice
We do not chase perfect numbers. And we treat the patient, not just their numbers. We look for patterns across symptoms, hormone balance, safety markers, and cardiometabolic risk. When something is off, we usually start by optimizing dose, injection frequency, sleep, recovery, and body composition before adding medications. The goal is a stable, sustainable plan that improves how you feel and performs well on objective monitoring.
Conclusion
TRT labs are not busywork. They are how we deliver precision therapy and keep patients safe while improving performance, body composition, and long-term health. Want a structured TRT monitoring plan built around your goals and risk factors? Contact Us today.
References
Figueiredo M, et al (2022). Testosterone Therapy With Subcutaneous Injections: A Safe, Practical, and Reasonable Option. J Clin Endocrinol Metab. 2022 Feb 17;107(3):614-626.
Mulhall J, et al (2018). Evaluation and management of testosterone deficiency: AUA guideline. J Urol Aug;200(2):423-432.
Bhasin S, Brito JP, Cunningham GR, et al (2018). Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. May 1;103(5):1715-1744.